In-Season Monitoring of Postharvest Rot Pathogens on European Pears (Pyrus communis) in Southern Oregon and Subsequent Management Strategies

Abstract

Postharvest decay in pears is a disease complex caused by several fungal pathogens. To understand the presence of these pathogens on flower and fruit tissues at early stages of fruit development, we collected samples from two commercial pear orchards in southern Oregon at five stages of fruit development: cluster bud, full bloom, petal fall, fruitlets, and field bins during commercial harvest. We recovered four common postharvest decay pathogens, Alternaria spp., Botrytis cinerea, Cladosporium herbarum, and Penicillium expansum, which varied in frequency across these stages, suggesting that pathogens may initially infect flowers and fruitlets well before conventional preharvest fungicide sprays. In a separate experiment, we applied four fungicides early in the growing season and/or shortly before harvest to determine when treatment was most effective in reducing the recovery rate of these pathogens and reducing storage rot. The recovery of Alternaria spp., B. cinerea, and P. expansum from flowers and fruitlets was reduced by 33, 47, and 33%, respectively, with bloom-time fungicide applications compared with nontreated control treatments. In addition, the fungicide program that included bloom-time application, preharvest application, and postharvest application resulted in significantly lower storage rot incidence compared with preharvest and postharvest application only. Syllit (dodine) reduced the storage rot incidence by 71%, Inspire Super (difenoconazole + cyprodinil) by 52%, Nevado (iprodione) by 36%, and Merivon (fluxapyroxad + pyraclostrobin) by 33% compared with nontreated control treatments.